First of all, you'd have to determine, if you really want a simple role-based-authentication (you may want to read: http://lostechies.com/derickbailey/2011/05/24/dont-do-role-based-authorization-checks-do-activity-based-checks/)
If you're sure it's absolutely sufficient, you're already on the right way with the SO link you provided in your question. It's kind of confusing that there is no support of 'roles' by default in Windows, but there are groups. Groups can be local or remote (e.g. ActiveDirectory), so an admin could assign users to certain groups, that are specific for your application (for an example look here: http://msdn.microsoft.com/en-us/library/ms731200(v=vs.110).aspx)
One key is: You have to prepare your application's central principal, hence fill it with roles, supported for the current user.
Therefore, On the very startup of your application you then check the current active user and set your application wide principal and role(s). This may look like this (just a very simple example):
using System;
using System.Collections.Generic;
using System.Linq;
using System.Security;
using System.Security.Principal;
using System.Text;
using System.Threading;
namespace WindowsPrincipalTrial
{
public class Program
{
// you could also move these definitions to a config file
private static IDictionary<string, string> _groupRoleMappings = new Dictionary<string, string>()
{
{"MYAPPUSERGRP", MyRoles.Standard},
{"MYAPPSUPPORTGRP", MyRoles.Extended},
{"MYAPPADMINGRP", MyRoles.Admin},
};
private static void Main(string[] args)
{
var windowsId = WindowsIdentity.GetCurrent();
if (windowsId != null)
{
var allRoleNames = getGroupCorrespondingRoles(windowsId);
var newPrincipal = new GenericPrincipal(windowsId, allRoleNames);
Thread.CurrentPrincipal = newPrincipal;
}
else
{
throw new NotSupportedException("There must be a logged on Windows User.");
}
}
private static string[] getGroupCorrespondingRoles(WindowsIdentity id)
{
// you also could do this more elegant with LINQ
var allMappedRoleNames = new List<string>();
string roleName;
foreach (var grp in id.Groups)
{
var groupName = grp.Translate(typeof(NTAccount)).Value.ToUpper();
if (_groupRoleMappings.TryGetValue(groupName, out roleName))
{
allMappedRoleNames.Add(roleName);
}
}
return allMappedRoleNames.ToArray();
}
}
public static class MyRoles
{
public const string Standard = "standard_role";
public const string Extended = "extended_role";
public const string Admin = "admin_role";
}
}
Then your Application-Principal is set up.
Now you could check access in your code like this:
public void DoSomethingSpecial()
{
if (Thread.CurrentPrincipal.IsInRole(MyRoles.Extended))
{
// do your stuff
}
else
{
// maybe display an error
}
}
Or more drastically:
public void DoSomethingCritical()
{
var adminPermission = new PrincipalPermission(null, MyRoles.Admin);
adminPermission.Demand();
// do stuff
}
what is possible even declarative, as known from ASP.NET:
[PrincipalPermission(SecurityAction.Demand, Role=MyRoles.Admin)]
public void DoSomethingMoreCritical()
{
// do stuff
}
The ugly thing with the latter two examples is, that they throw exceptions, when the right role isn't hit.
So the mapping between roles and groups you have to do quite at the start of your app, according to the systems you want to use (local groups, AD groups, LDAP groups etc.).
If you, however, prefer authentication with actions and roles, after all, have a look at Windows Identity Foundation and Claims Based Authorization! There are already some ready-to-use frameworks out there (e.g. https://github.com/thinktecture/Thinktecture.IdentityModel).
UPDATE:
When it comes to activity based and thereby claims based authorization, I will try in short, how you could achieve it, by using Thinktecture's IdentityModel.
Generally that approach still uses roles internally, but has a kind of translation layer in between. Thinktecture already encapsulates many things needed. Authorization checks in code are then done via claim permissions. They are technically kind of request for an access to a certain resource. For the sake of simplicity I limit my example for actions only, by using one single default resource (since ClaimPermission doesn't accept an empty resource).
If you want to use action@resource pairs, you'd have to modify the code respectively.
At first you need a ClaimsAuthorizationManager
public class MyClaimsAuthorizationManager : ClaimsAuthorizationManager
{
private IActivityRoleMapper _actionToRolesMapper;
public MyClaimsAuthorizationManager(IActivityRoleMapper mapper)
{
_actionToRolesMapper = mapper;
}
public override bool CheckAccess(AuthorizationContext context)
{
if (context == null)
{
throw new ArgumentNullException("context");
}
try
{
var action = getActionNameFromAuthorizationContext(context);
var sufficientRoles = _actionToRolesMapper.GetRolesForAction(action)
.Select(roleName => roleName.ToUpper());
var principal = context.Principal;
return CheckAccessInternal(sufficientRoles, principal);
}
catch (Exception ex)
{
return false;
}
}
protected virtual bool CheckAccessInternal(IEnumerable<string> roleNamesInUpperCase, IClaimsPrincipal principal)
{
var result = principal.Identities.Any(identity =>
identity.Claims
.Where(claim => claim.ClaimType.Equals(identity.RoleClaimType))
.Select(roleClaim => roleClaim.Value.ToUpper())
.Any(roleName => roleNamesInUpperCase.Contains(roleName)));
return result;
}
// I'm ignoring resources here, modify this, if you need'em
private string getActionNameFromAuthorizationContext(AuthorizationContext context)
{
return context.Action
.Where(claim => claim.ClaimType.Equals(ClaimPermission.ActionType))
.Select(claim => claim.Value)
.FirstOrDefault();
}
}
As you may have guessed, IActivityRoleMapper is an interface for a class, that returns the names of all roles, that include permission for a given action.
This class is very individual and I guess you'll find your way implementing it, because it's not the point here. You could do it by hardcoding, loading from xml or from a database. Also you would have to change/extend it, if you wanted to you action@resource pairs for permission requests.
Then you'd have to change the code in main() method to:
using Thinktecture.IdentityModel;
using Thinktecture.IdentityModel.Claims;
using Microsoft.IdentityModel.Web;
private static void Main(string[] args)
{
var windowsId = WindowsIdentity.GetCurrent();
if (windowsId != null)
{
var rolesAsClaims = getGroupCorrespondingRoles(windowsId)
.Select(role => new Claim(ClaimTypes.Role, role))
.ToList();
// just if you want, remember the username
rolesAsClaims.Add(new Claim(ClaimTypes.Name, windowsId.Name));
var newId = new ClaimsIdentity(rolesAsClaims, null, ClaimTypes.Name, ClaimTypes.Role);
var newPrincipal = new ClaimsPrincipal(new ClaimsIdentity[] { newId });
AppDomain.CurrentDomain.SetThreadPrincipal(newPrincipal);
var roleMapper = new ActivityRoleMapper(); // you have to implement
// register your own authorization manager, so IdentityModel will use it per default
FederatedAuthentication.ServiceConfiguration.ClaimsAuthorizationManager = new MyClaimsAuthorizationManager(roleMapper);
}
else
{
throw new NotSupportedException("There must be a logged on Windows User.");
}
}
Finally you can check access this way:
public const string EmptyResource = "myapplication";
public void DoSomethingRestricted()
{
if (!ClaimPermission.CheckAccess("something_restricted", EmptyResource))
{
// error here
}
else
{
// do your really phat stuff here
}
}
Or again, with exceptions:
private static ClaimPermission RestrictedActionPermission = new ClaimPermission(EmptyResource, "something_restricted");
public void DoSomethingRestrictedDemand()
{
RestrictedActionPermission.Demand();
// play up, from here!
}
Declarative:
[ClaimPermission(SecurityAction.Demand, Operation = "something_restricted", Resource = EmptyResource)]
public void DoSomethingRestrictedDemand2()
{
// dostuff
}
Hope this helps.
